Do hubs vacuum has anything to do with kingpin?

Recently, I noticed a leak on my right kingpin. Just before that for a while I was not able to engage to 4wd. (Some noise from under the car 4wd icon flashes and goes back with same reverse sound to 2WD)
While checking some youtube videos I have just learned that one of that it might fail to engage when vacuum is lost. 

I was in a sandy mud for a while before the last time it engaged, but nothing so dramatic or harsh. Light offroad. 

Just wondering if those two related deeply like the vacuum has to do with greasey joint, or is it the sand destroyed both? 
 

Chances are that the oil and grease mess inside the knuckle is probably causing it so cleaning it thoroughly when replacing the bearings will fix it, orrrrrrr it's a coincidence and there is a separate vacuum leak on one of the lines.